Tanakh is an acronym that is almost the same thing as saying the "Hebrew Bible."

It has three parts called the Torah, which has the first five books, the Nevi'im, which has the books of Hebrewprophets, and the Ketuvim, which has the rest of the books. It takes its name from the first (Hebrew) letter of each of these parts.

The Tanakh is the Jewish holy book, although most would say the Torah is, but it is just the most important part out of the three parts of the Tanakh.